EP2886329B1 - Packaging and method for producing a packaging - Google Patents

Packaging and method for producing a packaging Download PDF

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Publication number
EP2886329B1
EP2886329B1 EP13199378.4A EP13199378A EP2886329B1 EP 2886329 B1 EP2886329 B1 EP 2886329B1 EP 13199378 A EP13199378 A EP 13199378A EP 2886329 B1 EP2886329 B1 EP 2886329B1
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EP
European Patent Office
Prior art keywords
cover film
shell
layer
packaging according
sealing layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP13199378.4A
Other languages
German (de)
French (fr)
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EP2886329A1 (en
Inventor
Ralf Niepelt
Ulf Seifert
Robert Buitenhuis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mondi AG
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Mondi AG
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Publication date
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Priority to EP13199378.4A priority Critical patent/EP2886329B1/en
Publication of EP2886329A1 publication Critical patent/EP2886329A1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/16—Layered products comprising a layer of synthetic resin specially treated, e.g. irradiated
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/306—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl acetate or vinyl alcohol (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B32B27/327—Layered products comprising a layer of synthetic resin comprising polyolefins comprising polyolefins obtained by a metallocene or single-site catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/06—Interconnection of layers permitting easy separation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D77/00—Packages formed by enclosing articles or materials in preformed containers, e.g. boxes, cartons, sacks or bags
    • B65D77/10—Container closures formed after filling
    • B65D77/20—Container closures formed after filling by applying separate lids or covers, i.e. flexible membrane or foil-like covers
    • B65D77/2024—Container closures formed after filling by applying separate lids or covers, i.e. flexible membrane or foil-like covers the cover being welded or adhered to the container
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/31—Heat sealable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2435/00—Closures, end caps, stoppers
    • B32B2435/02—Closures, end caps, stoppers for containers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/40—Closed containers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/70—Food packaging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D51/00—Closures not otherwise provided for
    • B65D51/18—Arrangements of closures with protective outer cap-like covers or of two or more co-operating closures
    • B65D51/20—Caps, lids, or covers co-operating with an inner closure arranged to be opened by piercing, cutting, or tearing

Definitions

  • the invention relates to a package consisting of a tray and a cover sheet covering the tray, the tray having a layer of polyester adjoining the cover sheet and the cover sheet having at least one sealing layer made of a polymeric base substance adjoining the tray and with the tray by a separable one Sealed is connected.
  • the subject of the connection is also a method for producing such a packaging.
  • Such packaging has proven its worth above all for holding food, especially when it is perishable quickly and / or is to be stored in a well-sealed manner.
  • a peelable heat-seal seam enables a reliable closure and is at the same time easy to open for the end user.
  • a generic packaging with a film which can be used as a cover film together with a tray, for example for microwave menus.
  • the sealing layer of the cover film has a proportion of polyester and a proportion of organic and / or inorganic particles with an average diameter of 2 to 8 ⁇ m.
  • a film with such a sealing layer can be heat-sealed against PET, and the heat-sealed seam can be opened in a peelable manner. In this configuration, the particles have to be introduced into the polyester.
  • the effort involved in producing the sealing layer is also increased, since the layer thickness of the sealing layer is in the order of magnitude of the mean particle diameter.
  • the use of particles limits the processability of the top layer, since it does not consist of a material with continuous properties, but of a heterogeneous mixture.
  • the U.S. 5,888,599 describes a generic packaging with a shell and a three-layer cover film, an outer sealing layer of the cover film having a base polymer with a first portion of PET and a second polymer portion, based on a dicarboxylic acid, a diol or a mixture of the two substance classes.
  • An intermediate layer adjoining the sealing layer is made up of a polymer based on acrylic acid, methacrylic acid or an ester of these two compounds.
  • the use of polymers based on acrylic acid, as described for the intermediate layer is disadvantageous when the health-damaging properties of the monomers are taken into account. In addition, the raw materials described here are cost-intensive.
  • a generic packaging is also off EP 1 397 249 B1 known, according to which a multilayer cover sheet made of thermoplastic material with a sealing layer which has a low sealing initiation temperature is disclosed.
  • the cover film can be heat-sealed against various materials such as PP, PE, PVC, PS or PET.
  • the use of the cover film in conjunction with a tray as packaging is also described.
  • the film has at least a first intermediate layer and a sealing layer applied to the intermediate layer.
  • the first intermediate layer contains a terpolymer which is built up from an olefin, an unsaturated carboxylic acid or its ester and another (second) unsaturated carboxylic acid or its ester or anhydride.
  • the sealing layer contains, on the one hand, a copolymer of an olefin and an unsaturated carboxylic acid or its ester and, on the other hand, an additive.
  • This multilayer structure is based on the experience that polyolefins do not seal well against polyester and do not form a peelable seal, which is why the sealing layer has a copolymer with additives.
  • This embodiment has the disadvantage
  • the structure of the film is complicated, since the individual layers of the cover film are each made up of a co- or terpolymer and the materials described are expensive raw materials.
  • the invention is based on the object of realizing a package with a tray and a cover sheet, the tray having a layer of polyester, and the cover sheet being connected to the tray by a heat-sealed seam that can be separated and the cover sheet being as inexpensive as possible and is made up of simple raw materials.
  • the object is achieved in that the sealing layer has a polymeric base substance which has at least 20% by weight of polyethylene with a density of less than 0.92 g / cm 3 and that the sealing layer on the Shell-sealed side of the cover film has a surface modified by corona treatment.
  • a linear low density polyethylene (PE-LLDm) produced by metallocene catalysis is particularly well suited for use in the context of this invention.
  • cover films with a sealing layer according to the invention made of a polymeric base substance which contains at least 20% by weight of polyethylene with a density of less than 0.92 g / cm 3 and the surface to be sealed against the polyester was modified by corona treatment that such sealing layers can be sealed against polyester in a peelable manner. This is surprising, since a Corana treatment leads to a reduction in the sealability or seal strength in a polyethylene-polyethylene composite.
  • a surface can be passed through, for example, between two conductor elements serving as electrodes, with such a high voltage being applied between the electrodes that corona discharges take place.
  • the corona discharges ionize the air above the film surface, with ionized molecules in the air reacting with polymer molecules on the film surfaces, and with the accumulation of ions and / or partial cleavage of the polymer molecules creating polar areas on the essentially non-polar film surface, which causes it there is an increase in surface tension.
  • the surface modified by corona treatment as a sealing layer has a surface tension between 38 and 50 dynes / cm.
  • the surface tension can be set in a targeted manner via the intensity of the corona treatment. Without corona treatment, only very low sealing strengths are achieved for the sealing layer. However, particularly strong corona treatments carry the risk that the sealing layer can be damaged. In addition, the corona constancy can be improved by adding maleic anhydride to the sealing layer.
  • the surface tension is determined according to ISO 15989. Sealing tests have shown that for good sealing strengths or peel values, the surface tension of the sealing layer is between 38 and 50 dynes / cm (10 -3 N / m-Newtons per meter), particularly preferably between 44 and 48 dynes / cm.
  • sealing strength can be adjusted, in particular reduced, by blending the polymeric base substance of the sealing layer with other types of polyethylene.
  • the sealing strength can be tailored to the requirements in a targeted manner and freely selected over a wide range. So z. B. a particularly high seal strength can be selected for packaging that is exposed to high mechanical loads.
  • the sealing strength also depends on the sealing temperature.
  • the sealing layer according to the invention is distinguished by a wide sealing window based on the sealing temperature.
  • the temperature range in which the sealing strength lies within a specified range is referred to as the sealing window.
  • the sealing strength increases with increasing sealing temperature.
  • it is favorable that fluctuations in the sealing temperature essentially lead to the same sealing strength. Since the influence of temperature on the seal strength is small, the reproducibility of the seal seam properties is improved in the event of temperature fluctuations. For production, this means that if the sealing temperature fluctuates, the seal seam strength is within a specified range lies. As a result, production can be simplified and / or the throughput of production can be increased.
  • a test specification based on DIN 55529 can be used, with a test strip made of cover film and base layer (made from the material of the tray) being provided and heat-sealed in an area of 150 x 5 mm, with at least 20 mm unsealed (free) ends remain.
  • the test strips are divided into 95 x 15 mm pieces so that the heat-sealed seam runs approximately centrally along the width.
  • the free ends of the base layer are attached to a wheel and a free end of the cover sheet is attached to a pulling device, whereby the cover sheet is pulled off at a constant speed of 200 mm per minute at an angle of 90 °.
  • the peel force is determined by measuring the opening force when it is peeled off and is given in Newtons per 15 mm, corresponding to the width of the punched-out specimen. In the context of the invention, a peeling force between 2 and 15 Newtons per 15 mm sample width is to be achieved. Such a measurement can be used to evaluate not only the peeling force but also the peeling behavior due to the formation of shreds or the separation of layers.
  • polyethylene also means copolymers of ethylene and other alpha-olefins with a chain length of 4 to 8 carbon atoms.
  • the selection of the copolymer and in particular the choice of the monomers used influence the properties of the sealing layer, which is relevant in the context of this invention.
  • a copolymer made from ethylene and 1-octene has proven to be particularly advantageous because a sealing layer made from this copolymer shows good sealing properties even with a relatively low proportion of 1-octene, in particular a wide window with regard to the sealing temperature.
  • the seal seam strength is such when using one Copolymers largely dependent on the composition of the copolymer.
  • a proportion of 25% 1-octene can be sufficient, for example, to form a peelable sealing layer.
  • the mean melt flow index is a relevant material parameter within the scope of the invention.
  • the MFI is used to characterize the flow behavior of a polymer and can be determined according to ISO 1133 using a capillary rheometer.
  • the material to be tested is melted in a heated cylinder at a given constant temperature and pressed through a defined nozzle under the pressure of a test weight.
  • the measurements within the scope of the invention relate to a temperature of 190 ° C. and a test weight of 2.16 kg.
  • the MFI indicates the emerging mass of the polymer melt (the so-called extrudate) based on a certain time.
  • an MFI between 1.0 and 3.0 g per 10 minutes is particularly preferred for the polyethylene of the sealing layer. If the MFI is too high, there is a risk of blocking if the cover film is stored rolled up on rolls.
  • the cover film can also have further layers, the cover film or at least some of the layers of the cover film then being able to be produced by means of coextrusion.
  • adhesion promoter layers which preferably contain maleic anhydride (for example in a mixture with polyethylene).
  • a barrier layer, in particular against oxygen, can also be present, this preferably being based on ethylene vinyl alcohol (EVOH) based.
  • EVOH ethylene vinyl alcohol
  • An additional layer can also be provided for the cover film, preferably made of oriented PET (OPET), which is laminated on, for example, by a solvent-free or solvent-based two-component adhesive.
  • OPET oriented PET
  • BOPP biaxially excited polypropylene
  • the shell is made up of at least one polyester layer which adjoins the sealing layer of the cover film, with PET being used here as polyester, particularly preferably amorphous PET (APET).
  • PET being used here as polyester, particularly preferably amorphous PET (APET).
  • APET amorphous PET
  • One advantage of APET is, among other things. in high light transmission and good dimensional stability, which is why such trays are particularly suitable for holding food.
  • the shell is usually deep-drawn from a flat deep-drawing film.
  • the invention also relates to a method for producing a package according to claim 13.
  • the cover film is modified on a first surface of the sealing layer, which is adjacent to the tray, by means of a corona treatment.
  • the cover film can have additional layers, in which case the cover film or some of the layers of the cover film are produced by coextrusion.
  • the cover film can have laminated layers, preferably made of OPET, on the non-sealable surface. After the corona treatment, the cover film is sealed on the first surface with the formation of a sealing seam against the polyester layer of the shell.
  • an exemplary embodiment of the invention is shown on the basis of a figure:
  • an embodiment of the packaging is shown in cross section.
  • This shows a deep-drawn shell 1 which is covered with a cover film 2, the cover film 2 having a laminated composite of a coextruded coextrusion film 3 with a laminated outer layer 4, the laminated outer layer 4 consisting of OPET.
  • the coextrusion film 3 has a five-layer structure. Adjacent to the shell 1, the coextrusion film 3 has a 20 ⁇ m thick sealing layer as the first layer, followed by a 5 ⁇ m thick layer of PE and MAH. This is followed by a 5 ⁇ m thick layer that contains EVOH.
  • the figure shows a cover 6, which is fixed to the edge of the shell by means of a snap-on closure and extends over the cover film. In this way, the cover film can be protected against mechanical stress or unwanted damage.
  • the figure also shows schematically the picked up goods 7.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Wrappers (AREA)
  • Laminated Bodies (AREA)

Description

Die Erfindung betrifft eine Verpackung aus einer Schale und einer die Schale abdeckenden Deckfolie, wobei die Schale an die Deckfolie angrenzend eine Schicht aus Polyester aufweist und wobei die Deckfolie zumindest eine an die Schale angrenzende Siegelschicht aus einer polymeren Grundsubstanz aufweist und mit der Schale durch eine auftrennbare Siegelnaht verbunden ist. Gegenstand der Verbindung ist auch ein Verfahren zur Herstellung einer solchen Verpackung.The invention relates to a package consisting of a tray and a cover sheet covering the tray, the tray having a layer of polyester adjoining the cover sheet and the cover sheet having at least one sealing layer made of a polymeric base substance adjoining the tray and with the tray by a separable one Sealed is connected. The subject of the connection is also a method for producing such a packaging.

Derartige Verpackungen haben sich vor allem für die Aufnahme von Lebensmitteln bewährt, insbesondere wenn diese schnell verderblich sind und/oder gut abgedichtet gelagert werden sollen. Eine peelbare Heißsiegelnaht ermöglicht einen zuverlässigen Verschluss und ist gleichzeitig für den Endverbraucher einfach zu öffnen.Such packaging has proven its worth above all for holding food, especially when it is perishable quickly and / or is to be stored in a well-sealed manner. A peelable heat-seal seam enables a reliable closure and is at the same time easy to open for the end user.

Aus DE 103 52 444 A1 ist eine gattungsgemäße Verpackung mit einer Folie bekannt, die als Deckfolie zusammen mit einer Schale verwendet werden kann, beispielsweise für Mikrowellenmenüs. Die Siegelschicht der Deckfolie weist einen Anteil Polyester und einen Anteil organische und/oder anorganische Partikel mit einem mittleren Durchmesser von 2 bis 8 µm auf. Eine Folie mit einer solchen Siegelschicht ist heißsiegelbar gegen PET, wobei die Heißsiegelnaht peelbar geöffnet werden kann. Bei dieser Ausgestaltung müssen die Partikel in den Polyester eingebracht werden. Der Aufwand, die Siegelschicht herzustellen, wird zudem erhöht, da die Schichtdicke der Siegelschicht in der Größenordnung des mittleren Partikeldurchmesser liegt. Außerdem schränkt der Einsatz von Partikeln die Verarbeitbarkeit der Deckschicht ein, da diese nicht aus einem Material mit kontinuierlichen Eigenschaften besteht, sondern aus einer heterogenen Mischung.Out DE 103 52 444 A1 a generic packaging with a film is known which can be used as a cover film together with a tray, for example for microwave menus. The sealing layer of the cover film has a proportion of polyester and a proportion of organic and / or inorganic particles with an average diameter of 2 to 8 μm. A film with such a sealing layer can be heat-sealed against PET, and the heat-sealed seam can be opened in a peelable manner. In this configuration, the particles have to be introduced into the polyester. The effort involved in producing the sealing layer is also increased, since the layer thickness of the sealing layer is in the order of magnitude of the mean particle diameter. In addition, the use of particles limits the processability of the top layer, since it does not consist of a material with continuous properties, but of a heterogeneous mixture.

Die US 5 888 599 beschreibt eine gattungsgemäße Verpackung mit einer Schale und einer dreischichtigen Deckfolie, wobei eine außenliegende Siegelschicht der Deckfolie ein Basispolymer mit einem ersten Anteil PET und einem zweiten polymeren Anteil, basierend auf einer Dicarbonsäure, einem Diol oder einer Mischung der beiden Substanzklassen, aufweist. Eine an die Siegelschicht angrenzende Zwischenschicht ist aus einem Polymer auf Basis von Acrylsäure, Methacrylsäure oder einem Ester dieser beiden Verbindungen aufgebaut. Die Verwendung von Polymeren auf Basis von Acrylsäure, wie für die Zwischenschicht beschrieben, ist unter Berücksichtigung der gesundheitsschädlichen Eigenschaften der Monomere unvorteilhaft. Außerdem sind die hier beschriebenen Rohstoffe kostenintensiv.The U.S. 5,888,599 describes a generic packaging with a shell and a three-layer cover film, an outer sealing layer of the cover film having a base polymer with a first portion of PET and a second polymer portion, based on a dicarboxylic acid, a diol or a mixture of the two substance classes. An intermediate layer adjoining the sealing layer is made up of a polymer based on acrylic acid, methacrylic acid or an ester of these two compounds. The use of polymers based on acrylic acid, as described for the intermediate layer, is disadvantageous when the health-damaging properties of the monomers are taken into account. In addition, the raw materials described here are cost-intensive.

Eine gattungsgemäße Verpackung ist ebenso aus EP 1 397 249 B1 bekannt, gemäß welcher eine mehrschichtige Deckfolie aus thermoplastischem Kunststoff mit einer Siegelschicht, die eine niedrige Siegelanspringtemperatur aufweist, offenbart wird. Die Deckfolie kann gegen verschiedene Materialien wie PP, PE, PVC, PS oder PET heißgesiegelt werden. Ebenfalls beschrieben ist die Verwendung der Deckfolie in Verbindung mit einer Schale als Verpackung. Die Folie weist zumindest eine erste Zwischenschicht und eine auf die Zwischenschicht aufgebrachte Siegelschicht auf. Die erste Zwischenschicht enthält ein Terpolymer, welches aus einem Olefin, einer ungesättigten Carbonsäure bzw. deren Ester und einer anderen (zweiten) ungesättigten Carbonsäure bzw. deren Ester oder Anhydrid aufgebaut ist. Die Siegelschicht enthält einerseits ein Copolymer aus einem Olefin und einer ungesättigten Carbonsäure bzw. deren Ester und andererseits einen Zusatzstoff. Diese mehrschichtige Struktur geht auf die Erfahrung zurück, dass Polyolefine nicht gut gegen Polyester siegeln und keine peelbare Siegelnaht ausbilden, weshalb die Siegelschicht ein Copolymer mit Zusatzstoffen aufweist. Nachteilig ist bei dieser Ausführungsform allerdings, dass der Aufbau der Folie kompliziert ist, da die einzelnen Schichten der Deckfolie, jeweils aus einem Co- bzw. Terpolymer aufgebaut sind und die beschriebenen Materialien teuere Rohstoffe darstellen.A generic packaging is also off EP 1 397 249 B1 known, according to which a multilayer cover sheet made of thermoplastic material with a sealing layer which has a low sealing initiation temperature is disclosed. The cover film can be heat-sealed against various materials such as PP, PE, PVC, PS or PET. The use of the cover film in conjunction with a tray as packaging is also described. The film has at least a first intermediate layer and a sealing layer applied to the intermediate layer. The first intermediate layer contains a terpolymer which is built up from an olefin, an unsaturated carboxylic acid or its ester and another (second) unsaturated carboxylic acid or its ester or anhydride. The sealing layer contains, on the one hand, a copolymer of an olefin and an unsaturated carboxylic acid or its ester and, on the other hand, an additive. This multilayer structure is based on the experience that polyolefins do not seal well against polyester and do not form a peelable seal, which is why the sealing layer has a copolymer with additives. This embodiment has the disadvantage However, the structure of the film is complicated, since the individual layers of the cover film are each made up of a co- or terpolymer and the materials described are expensive raw materials.

Vor diesem Hintergrund liegt der Erfindung die Aufgabe zugrunde, eine Verpackung mit eine Schale und mit einer Deckfolie zu verwirklichen, wobei die Schale eine Schicht aus Polyester aufweist, und wobei die Deckfolie mit der Schale durch eine auftrennbare Heißsiegelnaht verbunden ist und wobei die Deckfolie möglichst kostengünstig und aus einfachen Rohstoffen aufgebaut ist.Against this background, the invention is based on the object of realizing a package with a tray and a cover sheet, the tray having a layer of polyester, and the cover sheet being connected to the tray by a heat-sealed seam that can be separated and the cover sheet being as inexpensive as possible and is made up of simple raw materials.

Ausgehend von einer Verpackung mit den eingangs beschriebenen Merkmalen wird die Aufgabe dadurch gelöst, dass die Siegelschicht eine polymere Grundsubstanz aufweist, die zumindest 20 Gew.-% Polyethylen einer Dichte kleiner 0,92 g/cm3 aufweist und dass die Siegelschicht an der auf die Schale aufgesiegelten Seite der Deckfolie eine durch Corona-Behandlung modifizierte Oberfläche aufweist.Starting from a package with the features described at the beginning, the object is achieved in that the sealing layer has a polymeric base substance which has at least 20% by weight of polyethylene with a density of less than 0.92 g / cm 3 and that the sealing layer on the Shell-sealed side of the cover film has a surface modified by corona treatment.

Ein durch Metallocen-Katalyse hergestelltes lineares Polyethylen niedriger Dichte (PE-LLDm) ist für die Verwendung im Rahmen dieser Erfindung besonders gut geeignet ist.A linear low density polyethylene (PE-LLDm) produced by metallocene catalysis is particularly well suited for use in the context of this invention.

Es ist bekannt, aneinandergrenzende Polyolefinschichten von Folien so auszugestalten, dass eine Verbindung in Form einer Heißsiegelnaht peelbar, d. h. ohne Zerstörung der Folien, vorhanden ist. Ein solcher Verbund ist beispielsweise in WO 2006/042856 beschrieben. Nach praktischen Erfahrungen kann jedoch eine Schicht auf Basis von Polyethylen nicht gut gegen Polyester gesiegelt werden.It is known to design adjoining polyolefin layers of foils in such a way that a connection in the form of a heat-sealed seam is peelable, ie without destroying the foils. Such a network is, for example, in WO 2006/042856 described. However, based on practical experience, a layer based on polyethylene cannot be sealed well to polyester.

Überraschenderweise führen Deckfolien mit einer erfindungsgemäßen Siegelschicht aus einer polymeren Grundsubstanz, die zumindest 20 Gew.-% Polyethylen einer Dichte kleiner 0,92 g/cm3 enthält, und wobei die Oberfläche die gegen den Polyester gesiegelt werden soll durch Corona-Behandlung modifiziert wurde dazu, dass derartige Siegelschichten gegen Polyester peelbar gesiegelt werden können. Dies ist überraschend, da eine Corana-Behandlung bei einem Polyethylen-Polyethylen-Verbund zu einer Herabsetzung der Siegelfähigkeit bzw. Siegelfestigkeit führt.Surprisingly, cover films with a sealing layer according to the invention made of a polymeric base substance which contains at least 20% by weight of polyethylene with a density of less than 0.92 g / cm 3 and the surface to be sealed against the polyester was modified by corona treatment that such sealing layers can be sealed against polyester in a peelable manner. This is surprising, since a Corana treatment leads to a reduction in the sealability or seal strength in a polyethylene-polyethylene composite.

Zur Corona-Behandlung kann eine Oberfläche beispielsweise zwischen zwei als Elektroden dienenden Leiterelementen hindurchgeführt werden, wobei zwischen den Elektroden eine so hohe Spannung angelegt ist, dass Corona-Entladungen stattfinden. Durch die Corona-Entladungen wird die Luft oberhalb der Folienoberfläche ionisiert, wobei ionisierte Moleküle der Luft mit Polymermolekülen der Folienoberflächen reagieren, und wobei durch Anlagerung von Ionen und/oder eine teilweise Spaltung der Polymermoleküle polare Bereiche auf der im Wesentlichen unpolaren Folienoberfläche entstehen, wodurch es zu einer Erhöhung der Oberflächenspannung kommt. Erfindungsgemäß ist vorgesehen, dass die durch Corona-Behandlung modifizierte Oberfläche als Siegelschicht eine Oberflächenspannung zwischen 38 und 50 dyn/cm aufweist.For corona treatment, a surface can be passed through, for example, between two conductor elements serving as electrodes, with such a high voltage being applied between the electrodes that corona discharges take place. The corona discharges ionize the air above the film surface, with ionized molecules in the air reacting with polymer molecules on the film surfaces, and with the accumulation of ions and / or partial cleavage of the polymer molecules creating polar areas on the essentially non-polar film surface, which causes it there is an increase in surface tension. According to the invention it is provided that the surface modified by corona treatment as a sealing layer has a surface tension between 38 and 50 dynes / cm.

Über die Intensität der Corona-Behandlung kann die Oberflächenspannung gezielt eingestellt werden. Ohne Corona-Behandlung werden für die Siegelschicht nur sehr geringe Siegelfestigkeiten erreicht. Besonders starke Corona-Behandlungen birgt allerdings die Gefahr, dass die Siegelschicht beschädigt werden kann. Zusätzlich kann die Corona-Konstanz durch Zugabe von Maleinsäureanhydrid zur Siegelschicht verbessert werden.The surface tension can be set in a targeted manner via the intensity of the corona treatment. Without corona treatment, only very low sealing strengths are achieved for the sealing layer. However, particularly strong corona treatments carry the risk that the sealing layer can be damaged. In addition, the corona constancy can be improved by adding maleic anhydride to the sealing layer.

Die Oberflächenspannung ist gemäß ISO 15989 bestimmt. Siegelversuche haben gezeigt, dass für gute Siegelfestigkeiten bzw Peelwerte die Oberflächenspannung der Siegelschicht zwischen 38 und 50 dyn/cm (10-3 N/m - Newton pro Meter), besonders bevorzugt zwischen 44 und 48 dyn/cm beträgt.The surface tension is determined according to ISO 15989. Sealing tests have shown that for good sealing strengths or peel values, the surface tension of the sealing layer is between 38 and 50 dynes / cm (10 -3 N / m-Newtons per meter), particularly preferably between 44 and 48 dynes / cm.

Auch eine genaue Einstellung und ggf. Erniedrigung der Siegelfestigkeit ist im Rahmen der Erfindung möglich. Durch einen Verschnitt der polymeren Grundsubstanz der Siegelschicht mit anderen Polyethylen-Typen kann die Siegelfestigkeit eingestellt, insbesondere verringert werden.A precise setting and, if necessary, a reduction in the sealing strength is also possible within the scope of the invention. The sealing strength can be adjusted, in particular reduced, by blending the polymeric base substance of the sealing layer with other types of polyethylene.

Durch die zuvor genannten Modifikationen der Siegelschicht kann die Siegelfestigkeit in einem weiten Bereich auf die Erfordernisse gezielt abgestimmt und frei gewählt werden. So z. B. kann für Verpackungen, die hohen mechanischen Belastungen ausgesetzt sind, eine besonders hohe Siegelfestigkeit gewählt werden.As a result of the aforementioned modifications of the sealing layer, the sealing strength can be tailored to the requirements in a targeted manner and freely selected over a wide range. So z. B. a particularly high seal strength can be selected for packaging that is exposed to high mechanical loads.

Die Siegelfestigkeit ist auch von der Siegeltemperatur abhängig. In diesem Zusammenhang zeichnet sich die erfindungsgemäße Siegelschicht durch ein breites Siegelfenster bezogen auf die Siegeltemperatur aus. Als Siegelfenster wird dabei der Temperaturbereich bezeichnet, in dem die Siegelfestigkeit innerhalb eines vorgegebenen Bereichs liegt. Im Allgemeinen steigt die Siegelfestigkeit mit zunehmender Siegeltemperatur. Es ist für die technische Umsetzung der Herstellung allerdings günstig, dass Schwankungen der Siegeltemperatur im Wesentlichen zu der selben Siegelfestigkeit führen. Da der Einfluss der Temperatur auf die Siegelfestigkeit gering ausfällt, ist die Reproduzierbarkeit der Siegelnahteigenschaften bei Temperaturschwankungen verbessert. Für die Herstellung bedeutet dies, dass bei Temperaturschwankungen der Siegeltemperatur die Siegelnahtfestigkeit in einem vorgegebenen Bereich liegt. Dadurch kann die Produktion vereinfacht werden und/oder der Durchsatz der Produktion erhöht werden.The sealing strength also depends on the sealing temperature. In this context, the sealing layer according to the invention is distinguished by a wide sealing window based on the sealing temperature. The temperature range in which the sealing strength lies within a specified range is referred to as the sealing window. In general, the sealing strength increases with increasing sealing temperature. For the technical implementation of the production, however, it is favorable that fluctuations in the sealing temperature essentially lead to the same sealing strength. Since the influence of temperature on the seal strength is small, the reproducibility of the seal seam properties is improved in the event of temperature fluctuations. For production, this means that if the sealing temperature fluctuates, the seal seam strength is within a specified range lies. As a result, production can be simplified and / or the throughput of production can be increased.

Zur Messung der Siegelfestigkeit kann beispielsweise eine an die DIN 55529 angelehnte Prüfvorschrift verwendet werden, wobei ein Teststreifen aus Deckfolie und Grundschicht (aus dem Material der Schale) bereitgestellt wird, und in einem Bereich von 150 x 5 mm heißgesiegelt wird, wobei mindestens 20 mm ungesiegelte (freie) Enden verbleiben. Die Teststreifen werden in 95 x 15 mm große Stücke zerteilt, so dass die Heißsiegelnaht in etwa mittig entlang der Breite verläuft. Die freien Enden der Grundschicht werden auf einem Rad befestigt und ein freies Ende der Deckfolie wird an einer Zugvorrichtung befestigt, wodurch die Deckfolie mit einer konstanten Geschwindigkeit von 200 mm pro Minute in einem Winkel von 90° abgezogen wird. Die Peelkraft wird durch Messung der Öffnungskraft beim Abziehen bestimmt und in Newton pro 15 mm entsprechend der Breite des ausgestanzten Probekörpers angegeben. Im Rahmen der Erfindung soll eine Peelkraft zwischen 2 und 15 Newton pro 15 mm Probenbreite erreicht werden. Aus einer solchen Messung können neben der Peelkraft auch das Peelverhalten durch Fetzenbildung oder Schichtentrennung, bewertet werden.To measure the seal strength, for example, a test specification based on DIN 55529 can be used, with a test strip made of cover film and base layer (made from the material of the tray) being provided and heat-sealed in an area of 150 x 5 mm, with at least 20 mm unsealed (free) ends remain. The test strips are divided into 95 x 15 mm pieces so that the heat-sealed seam runs approximately centrally along the width. The free ends of the base layer are attached to a wheel and a free end of the cover sheet is attached to a pulling device, whereby the cover sheet is pulled off at a constant speed of 200 mm per minute at an angle of 90 °. The peel force is determined by measuring the opening force when it is peeled off and is given in Newtons per 15 mm, corresponding to the width of the punched-out specimen. In the context of the invention, a peeling force between 2 and 15 Newtons per 15 mm sample width is to be achieved. Such a measurement can be used to evaluate not only the peeling force but also the peeling behavior due to the formation of shreds or the separation of layers.

Unter Polyethylen sind im Rahmen der Erfindung auch Copolymere aus Ethylen und anderen Alpha-Olefinen mit einer Kettenlänge von 4 bis 8 Kohlenstoffatomen gemeint. Die Auswahl des Copolymers und insbesondere die Wahl der eingesetzten Monomere beeinflussen die Eigenschaften der Siegelschicht, was im Rahmen dieser Erfindung relevant ist. Als besonders günstig hat sich hierbei ein Copolymer aus Ethylen und 1-Octen herausgestellt, weil eine Siegelschicht aus diesem Copolymer bereits bei einem relativ geringen Anteil an 1-Octen gute Siegeleigenschaften zeigt, insbesondere ein breites Fenster bezüglich der Siegeltemperatur. Die Siegelnahtfestigkeit ist bei Verwendung eines derartigen Copolymers maßgeblich von der Zusammensetzung des Copolymers abhängig. Ein Anteil von 25 % 1-Octen kann beispielsweise zur Ausbildung einer peelbaren Siegelschicht ausreichen. Durch unterschiedliches Abmischen des Copolymers sind sowohl Siegelnahtfestigkeit, als auch Siegeltemperatur gut einstellbar, wobei das Temperaturfenster, in dem ein gewisser Siegelnahtfestigkeitsbereich erreicht wird, durch die Charakteristik des Copolymers besonders groß ist.In the context of the invention, polyethylene also means copolymers of ethylene and other alpha-olefins with a chain length of 4 to 8 carbon atoms. The selection of the copolymer and in particular the choice of the monomers used influence the properties of the sealing layer, which is relevant in the context of this invention. A copolymer made from ethylene and 1-octene has proven to be particularly advantageous because a sealing layer made from this copolymer shows good sealing properties even with a relatively low proportion of 1-octene, in particular a wide window with regard to the sealing temperature. The seal seam strength is such when using one Copolymers largely dependent on the composition of the copolymer. A proportion of 25% 1-octene can be sufficient, for example, to form a peelable sealing layer. By mixing the copolymer differently, both the seal seam strength and the sealing temperature can be easily adjusted, the temperature window in which a certain seal seam strength range is achieved being particularly large due to the characteristics of the copolymer.

Neben der Dichte ist der mittlere Schmelzflussindex (MFI) eine im Rahmen der Erfindung relevante Materialkenngröße. Der MFI dient der Charakterisierung des Fließverhaltens eines Polymers und kann nach ISO 1133 mittels eines Kapillarrheometers ermittelt werden. Dabei wird das zu prüfende Material in einem beheizbaren Zylinder bei einer vorgegebenen konstanten Temperatur aufgeschmolzen und unter Druck eines Prüfgewichts durch eine definierte Düse gedrückt. Die Messungen im Rahmen der Erfindung beziehen sich auf eine Temperatur von 190 °C und ein Prüfgewicht von 2,16 kg. Der MFI gibt die austretende Masse der Polymerschmelze (des sogenannten Extrudats) bezogen auf eine bestimmte Zeit an. Im Rahmen der Erfindung ist für das Polyethylen der Siegelschicht ein MFI zwischen 1,0 und 3,0 g pro 10 Minuten besonders bevorzugt. Bei einem zu hohen MFI besteht die Gefahr des Verblockens wenn die Deckfolie auf Rollen aufgewickelt gelagert wird.In addition to the density, the mean melt flow index (MFI) is a relevant material parameter within the scope of the invention. The MFI is used to characterize the flow behavior of a polymer and can be determined according to ISO 1133 using a capillary rheometer. The material to be tested is melted in a heated cylinder at a given constant temperature and pressed through a defined nozzle under the pressure of a test weight. The measurements within the scope of the invention relate to a temperature of 190 ° C. and a test weight of 2.16 kg. The MFI indicates the emerging mass of the polymer melt (the so-called extrudate) based on a certain time. In the context of the invention, an MFI between 1.0 and 3.0 g per 10 minutes is particularly preferred for the polyethylene of the sealing layer. If the MFI is too high, there is a risk of blocking if the cover film is stored rolled up on rolls.

Die Deckfolie kann neben der erfindungsgemäßen Siegelschicht noch weitere Schichten aufweisen, wobei die Deckfolie, oder zumindest ein Teil der Schichen der Deckfolie dann mittels Coextrusion hergestellt sein können. Bei mehrschichtigen Deckfolien können zusätzlich Haftvermittlerschichten vorhanden sein, die vorzugsweise Maleinsäureanhydrid (beispielsweise in Mischung mit Polyethylen) enthalten. Ebenso kann eine Barriereschicht, insbesondere gegen Sauerstoff, vorhanden sein, wobei diese vorzugsweise auf Ethylenvinylalkohol (EVOH) basiert. Gerade für die Verpackung von verderblichen Lebensmitteln ist die Verwendung von Sauerstoffbarriereschichten zweckmäßig, um die Haltbarkeit und Qualität der aufgenommen Lebensmittel bestmöglich zu gewährleisten.In addition to the sealing layer according to the invention, the cover film can also have further layers, the cover film or at least some of the layers of the cover film then being able to be produced by means of coextrusion. In the case of multi-layer cover films, there may also be adhesion promoter layers which preferably contain maleic anhydride (for example in a mixture with polyethylene). A barrier layer, in particular against oxygen, can also be present, this preferably being based on ethylene vinyl alcohol (EVOH) based. The use of oxygen barrier layers is particularly useful for packaging perishable food in order to ensure the best possible shelf life and quality of the food ingested.

Für die Deckfolie kann auch noch eine zusätzliche Schicht vorgesehen sein, vorzugsweise aus orientiertem PET (OPET), die beispielsweise durch einen lösemittelfreien oder lösemittelbasierten Zwei-Komponentenkleber aufkaschiert ist. Anstelle von OPET kann auch biaxialgeregtes Polypropylen (BOPP) eingesetzt werden.An additional layer can also be provided for the cover film, preferably made of oriented PET (OPET), which is laminated on, for example, by a solvent-free or solvent-based two-component adhesive. Instead of OPET, biaxially excited polypropylene (BOPP) can also be used.

Die Schale ist zumindest aus einer Polyesterschicht aufgebaut, die an die Siegelschicht der Deckfolie angrenzt, wobei als Polyester hier bevorzugt PET, besonders bevorzugt amorphes PET (APET) zum Einsatz kommt. Ein Vorteil von APET liegt u. a. in einer hohen Lichtdurchlässigkeit und einer guten Formstabilität, weshalb sich derartige Schalen besonders zur Aufnahme von Lebensmitteln eignen. Im Rahmen der Erfindung ist die Schale in der Regel aus einer ebenen Tiefziehfolie tiefgezogen.The shell is made up of at least one polyester layer which adjoins the sealing layer of the cover film, with PET being used here as polyester, particularly preferably amorphous PET (APET). One advantage of APET is, among other things. in high light transmission and good dimensional stability, which is why such trays are particularly suitable for holding food. In the context of the invention, the shell is usually deep-drawn from a flat deep-drawing film.

Gegenstand der Erfindung ist auch ein Verfahren zur Herstellung einer Verpackung gemäß Anspruch 13. Die Deckfolie wird an einer ersten Oberfläche der Siegelschicht, die an die Schale angrenzt, durch eine Corona-Behandlung modifiziert. Die Deckfolie kann zusätzliche Schichten aufweisen, wobei in diesem Fall die Deckfolie bzw. ein Teil der Schichten der Deckfolie durch Coextrusion hergestellt sind. Ebenso kann die Deckfolie im Rahmen der Erfindung an der nichtsiegelbaren Oberfläche aufkaschierte Schichten aufweisen, vorzugsweise aus OPET. Die Deckfolie wird nach der Corona-Behandlung an der ersten Oberfläche unter Bildung einer Siegelnaht gegen die Polyesterschicht der Schale gesiegelt.The invention also relates to a method for producing a package according to claim 13. The cover film is modified on a first surface of the sealing layer, which is adjacent to the tray, by means of a corona treatment. The cover film can have additional layers, in which case the cover film or some of the layers of the cover film are produced by coextrusion. Likewise, within the scope of the invention, the cover film can have laminated layers, preferably made of OPET, on the non-sealable surface. After the corona treatment, the cover film is sealed on the first surface with the formation of a sealing seam against the polyester layer of the shell.

Anhand einer Abbildung wird ein Ausführungsbeispiel der Erfindung gezeigt:
In der einzigen Figur ist ein Ausführungsbeispiel der Verpackung im Querschnitt dargestellt. Diese zeigt eine Tiefziehschale 1, die mit einer Deckfolie 2 abgedeckt ist, wobei die Deckfolie 2 einen Kaschierverbund einer coextrudierten Coextrusionsfolie 3 mit einer aufkaschierten Außenschicht 4 aufweist, wobei die aufkaschierte Außenschicht 4 aus OPET besteht. Die Coextrusionsfolie 3 weist eine fünfschichtige Struktur auf. Angrenzend an die Schale 1 weist die Coextrusionsfolie 3 als erste Schicht eine 20 µm dicke Siegelschicht auf, gefolgt von einer 5 µm dicken Schicht aus PE und MAH. Danach folgt eine 5µm dicke Schicht, welche EVOH enthält. Darauf folgt eine 5µm dicke Schicht aus Polyethylen und MAH. Abgeschlossen wird die Coextrusionsfolie durch eine 15µm Schicht, die PE enthält. Die Siegelschicht bildet entlang des abgeflachten Randes der Schale 1 eine Siegelnaht 5 aus. Zusätzlich zeigt die Figur noch einen Deckel 6, der über einen Snap-on-Verschluss am Rand der Schale fixiert ist und sich über die Deckfolie erstreckt. Dadurch kann die Deckfolie gegen mechanische Belastung oder die ungewollte Beschädigung geschützt werden. Die Abbildung zeigt auch schematisch die aufgenommene Ware 7.An exemplary embodiment of the invention is shown on the basis of a figure:
In the single figure, an embodiment of the packaging is shown in cross section. This shows a deep-drawn shell 1 which is covered with a cover film 2, the cover film 2 having a laminated composite of a coextruded coextrusion film 3 with a laminated outer layer 4, the laminated outer layer 4 consisting of OPET. The coextrusion film 3 has a five-layer structure. Adjacent to the shell 1, the coextrusion film 3 has a 20 μm thick sealing layer as the first layer, followed by a 5 μm thick layer of PE and MAH. This is followed by a 5 µm thick layer that contains EVOH. This is followed by a 5 µm thick layer of polyethylene and MAH. The coextrusion film is closed by a 15 µm layer that contains PE. The sealing layer forms a sealing seam 5 along the flattened edge of the shell 1. In addition, the figure shows a cover 6, which is fixed to the edge of the shell by means of a snap-on closure and extends over the cover film. In this way, the cover film can be protected against mechanical stress or unwanted damage. The figure also shows schematically the picked up goods 7.

Claims (12)

  1. A packaging comprising a shell (1) and a cover film (2) covering the shell (1), wherein the shell (1) has a layer of polyester adjacent to the cover film (2) and wherein the cover film (2) has at least one sealing layer made of a polymeric basic substance adjacent to the shell (1) and is connected to the shell by a separable heat sealing seam (5), characterized in that the basic substance comprises at least 20 wt.% of polyethylene having a density of less than 0.92 g/cm3 and that on the side of the cover film (2) sealed onto the shell (1) the sealing layer has a surface modified by corona treatment, wherein the surface of the sealing layer modified by corona treatment has a surface tension between 38 and 50 dyn/cm in accordance with ISO 15989.
  2. The packaging according to Claim 1, characterized in that the polyethylene fraction of the basic substance which has a density of less than 0.92 g/cm3, has a mean flow index (MFI) of 1.0 to 3.0 g/10 min. determined in accordance with ISO 1133 at a temperature of 190 °C and a test weight of 2.16 kg.
  3. The packaging according to Claim 1 or 2, characterized in that the polyethylene fraction of the basic substance which has a density of less than 0.92 g/cm3, is a low-density metallocene-catalyzed linear polyethylene (PE-LLDm).
  4. The packaging according to one of Claims 1 to 3, characterized in that the polyethylene fraction of the basic substance which has a density of less than 0.92 g/cm3, is a copolymer of ethylene and a further olefin, wherein the second olefin has a chain length of 4 to 8 carbon atoms.
  5. The packaging according to Claim 4, characterized in that the second olefin has a chain length of 8 carbon atoms.
  6. The packaging according to one of Claims 1 to 5, characterized in that the sealing layer consists completely of polyolefin.
  7. The packaging according to one of Claims 1 to 6, characterized in that the layer of the shell (1) adjoining the cover film (2) comprises amorphous PET (APET) .
  8. The packaging according to one of Claims 1 to 7, characterized in that the cover film (2) contains a barrier layer based on ethylene vinyl alcohol (EVOH).
  9. The packaging according to one of Claims 1 to 8, characterized in that the cover film (2) comprises at least two layers produced by coextrusion.
  10. The packaging according to one of Claims 1 to 9, characterized in that the heat sealing layer (5) has an opening force between 2 and 15 Newtons per 15 mm determined during a withdrawal of the cover film (2) from the shell (1) at 90 .
  11. The packaging according to one of Claims 1 to 10, characterized in that the shell (1) is deep drawn.
  12. A method for producing a packaging from a shell (1) and a cover film (2) according to one of Claims 1 to 11, which includes the following steps:
    supplying a shell which has at least one external polyester layer;
    supplying a cover film (2) which on a first surface has a sealing layer of a polymeric basic substance comprising at least 20 wt.% of polyethylene having a density of less than 0.92 g/cm3,
    modifying the first surface of the cover film (2) by corona treatment, wherein the surface of the sealing layer modified by corona treatment has a surface tension between 38 and 50 dyn/cm in accordance with ISO 15989;
    sealing the corona-treated first surface of the cover film (2) towards the polyester layer of the shell (1).
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